In an aircraft provided with an electronic flight management system, the crew of an aircraft (pilot-in-command and co-pilot) moves around in a loaded cognitive environment. In practice, it is subject to many visual and auditory stimuli.
These stimuli are as follows:
Visual:                screens displaying different pages,        control panels,        indicators on the ceiling panel,        knob positions (“C/B”, selector switch, etc.),        “Master Warning” or “Master Caution” (warnings),        
Audio:                operational alerts (“PULL UP”, “TERRAIN” from the “TAWS”, altitude announcement when landing),        audio alerts in the event of failure: “single chime” or “continuous repetitive chime” (single or continuous repetitive alerts),        ATC (Air Traffic Control),        Messages issued by the airline: management of the CC (cabin crew), and so on,        
Sensitive:                “Shaker” (in stall cases).        
It will also be noted that smell may add stress (case of fire, or smoke, etc).
Also, in order to manage the various systems and handle the basic piloting of the aircraft, the crew must perform the following various tasks, concurrently:                primary controls: control column, rudder bar, engine power, propeller pitch, compensator, and so on,        regular check on flight safety: primary flight parameters (engine, speed, attitude), environment (other aircraft, terrain, etc.), management of failures (procedures to be carried out in the event of failure),        navigation (precise/complex information to be entered by the crew, such as the flight plan),        ATC (passive listening to commands from the controller and active dialogue with the controller),        management of messages issued by the airline managing the aircraft (“ACARS” messages),        passenger and cabin crew information.        
While all these tasks are being carried out, the crew may be interrupted. The systems must be made so as not to overload the work of the crew, by giving indications that are precise (no thought needed to specify a requested action) and reliable (the crew must not question the indication made by the system).
In the case of the FWS (flight warning system), the procedures request performance of the action “as required” (the pilot must himself determine the correct position or action, the requested action being true in more than 90% of cases, but, in a few remaining cases, the action to be carried out is different).
Also, two different procedures may arise in the same flight and have an item in common for which the requested action is different and therefore inconsistent. The first of these procedures corresponds to the case where the action to be carried out is the same in most cases, therefore the procedure contains this action. In this case, the manufacturer of the system assumes that the pilot can exercise his critical faculty and conduct an action that is different from the requested action if he considers that this requested action is not suited to the situation. In the second case, the action to be carried out for the current procedure depends on the situation (state of the aircraft, surrounding conditions, etc.), and the procedure requests the action to be carried out “as required”. In both these cases, the pilot must carry out a cognitive action, whereas from his training he is primarily accustomed to automatic procedures.
Thus, the crew has to be aware of the state of the aircraft in order to deal with certain requested actions.
The current flight management systems have the following characteristics:                Auto-acknowledgement of certain lines of the procedure, because the system detects the correct state linked to the requested action (dynamic modification of the style of presentation of a line).        Non-presentation of a line when there is no action to be carried out (dynamic presentation or non-presentation of a line).        